Stimulant use is prevalent among men who have sex with men (MSM) and is associated with sub-optimal adherence to antiretroviral therapy (ART), poor clinical outcomes, and sexual risk-taking. Moreover, MSM represent a unique population, whose intervention needs vary from their heterosexual counterparts. For these reasons, HIV-positive stimulant-using MSM (HIV+ SU-MSM) require ART adherence interventions tailored to their unique context, concerns, and lifestyle. Despite this urgent need, no technology-based ART adherence interventions specifically tailored to the needs of HIV+ SU-MSM have been developed and assessed for feasibility and acceptability with this population. We will use a three-phase approach to develop and assess the feasibility and acceptability of a smart phone application (app) ART adherence intervention tailored to the needs of HIV+ SU-MSM and grounded in the Information-Motivation-Behavioral Skills (IMB) model. Aim 1 will consist of 4 online focus groups (8-10 men each) to identify smart phone app contents and functions to maximize interest among HIV+ SU-MSM in downloading an ART adherence app, initiating its use, and maintaining engagement with the app over time. In addition, focus group participants will be asked to describe their ART adherence informational, motivational and behavioral skills needs. Lessons from the focus groups will be used in Aim 2 to develop a novel smart phone app tailored to HIV+ SU-MSM to improve their ART adherence. Intervention components will consist of tailored informational messages, a motivational personal intervention guide, medication reminders, ART and drug use self-monitoring, self-reflection and strategy rehearsal. The intervention will be usability tested among five participants prior to finalizing the look and content. The developed intervention will be pilot tested among 76 HIV+ SU-MSM in Aim 3. HIV+ SU-MSM randomized to the intervention group (n=38) will participate in the smart phone app intervention for 60 days, while control group (n=38) participants will receive treatment-as-usual through their existing medical care. Group adherence outcomes will be compared at baseline, post-intervention, and 3- and 6-month follow-up. Among participants randomized to the intervention group, daily patterns during the intervention period will be examined to assess app component use, percent of ART doses taken, rating of suggested strategies to overcome adherence barriers, experiences of drug cravings and use of stimulants. These and other feasibility (e.g. days per week accessing the intervention, overall retention) and acceptability (e.g., self-reported acceptability and user engagement) measures will be collected throughout the study period to inform a subsequent large scale RCT trial. The primary significance of the proposed research to public health is to improve ART adherence among substance-using populations and reduce rates of HIV transmission among MSM. If found effective, the smart phone app intervention will be readily available for scale-up for national dissemination through partnering with HIV clinics in high-burden regions, and in low-resource and rural areas.